The present invention relates generally to a security seal of the padlock-type and, more particularly to a seal having a wire shackle that is first threaded through a structure to be secured and then locked in a body under a torsional force such that the seal must be broken to be opened.
Padlock-type security seals have found widespread use as a means for securing electric meters and the like. Such seals generally include a plastic body with a pair of apertures opening at one end of the body and a shackle formed of a piece of U-shaped wire having legs with reversibly bent end portions. When the seal is put into use, the shackle legs are first threaded through a structure to be secured, such as a retaining ring fitted around a cover for an electric meter. The shackle legs are then inserted into the body apertures whereby the reversibly bent end portions engage some form of inner structure of the body for permanent retention. A lateral pulling force on the shackle only forces the reversibly bent end portions into stronger engagement with the body. Thus, the shackle must be severed or otherwise broken to open the seal.
In addition to the usual locking mechanisms, most seals include some form of tamper-indicating structure. Generally, tamper-indicating structures are designed such that any significant attempts to defeat or tamper with the seal will normally result in altering the seal in such a manner that the attempt will be readily detectable. For example, U.S. Pat. No. 4,893,853 to Guiler discloses a seal having taper-indicating means which causes the shackle ends to break through the walls of the body when an attempt is made to remove the shackle. U.S. Pat. No. 4,836,590 to Swift discloses a body having a brightly colored insert retained in the body. The insert retains the ends of the shackle and includes a frangible member that is fractured upon an attempt to remove the shackle. Such damage in both devices is readily apparent thereby indicating evidence of tampering.
Although such devices have served the purpose, they have not provided entirely satisfactory results, because some efforts to defeat such structures by picking have proved successful. One such method of picking involves inserting a picking tool into the seal body and deforming the shackle legs to an extent that the legs can freely be withdrawn from the sealed body, reformed, and later replaced in the seal body. Numerous efforts have been made to prevent picking as well. For example, U.S. Pat. No. 3,375,033 to Moberg discloses a shackle having reversibly bent portions that block insertion of a picking tool into the apertures of the body.
Although such efforts have proven reasonably successful, it is desirable to provide an inexpensive and easily installed single-use seal designed to strongly secure a structure and to both resist tampering and to permit easy detection of any tampering.
The present invention is a padlock-type security seal that generally includes a U-shaped resilient shackle having two legs and a body having two apertures formed in a first end thereof for insertion of the shackle legs. The apertures are positioned in the first end of the body to provide a torsional force to the shackle upon insertion. The torsional force acts on locking elements of the legs to engage the body thereby preventing removal of the shackle.
The locking elements of the shackle legs are preferably reversibly bent tangs formed at opposite offset angles with respect to the plane of the shackle. The apertures are preferably generally rectangular in cross-section and the major axes of the rectangular apertures are positioned in the first end of the body along two separate offset planes thereby providing the torsional force to the shackle. At least one of the shackle legs also preferably includes a bent hinge portion for transferring the torsional force to the locking elements. The shackle legs further preferably include inwardly bent portions for substantially occluding the leg insertion apertures to prevent insertion of a picking tool.
The seal further preferably includes a locking insert contained within the body for engaging at least one of the locking elements of the shackle legs under the torsional force to prevent removal of the shackle. The locking insert is inserted into a third aperture formed in a second end of the body opposite the first end that is in fluid communication with the other apertures. The locking insert includes at least one slot formed therethrough for engaging the locking element and preferably includes two slots forming an X-shaped aperture through the locking insert. For tamper indicating purposes, the body is preferably translucent while the locking insert is preferably opaque.
For a better understanding of the present invention, reference is made to the following detailed description, taken in conjunction with the accompany drawings and its scope will be defined in the appended claims.